Food & Water Safety

Investigators

• Andy Potter, Wolfgang Koester, Brenda Allan

Background:

Pathogens transmitted from animals to humans via contaminated food and water cause up to 33 million cases of reported illness each year in North America. Recent estimates suggest that direct or indirect animal to human transmission of pathogens accounts for up to 50% of human infectious disease in developed countries. Six bacterial species account for over one half of the economic losses, including Campylobacter jejuni, Escherichia coli O157:H7 (and other non-O157 STEC serotypes), non-typhoid Salmonella, Listeria monocytogenes, Clostridium perfringens, and Staphylococcus aureus. Many human pathogens do not cause disease in their animal hosts, making their detection difficult. For example, most chickens are exposed to C. jejuni and/or S. enterica serovar Enteritidis (Salmonella Enteritidis) during their life, but exposure does not result in any clinical signs of infection. E. coli O157:H7 has been reported to cause intestinal lesions in experimentally-infected neonatal calves, but does not affect adult cattle.

Control of food and water borne pathogens:

The development and implementation of biological control methods for food and water-borne pathogens is relatively new, having been carried out in the past primarily by inspection of food products and water supplies rather than direct intervention measures aimed at preventing contamination. Current strategies employed by industry and regulatory agencies involve control procedures at key points in the animal and food production chain, including on-farm, at slaughter, processing, etc. These are collectively referred to as Hazard Analysis and Critical Control Points (HACCP). Vaccines have been used for centuries for the prevention of infectious diseases, but only recently has there been interest in using them to specifically prevent colonization of the host in which no disease occurs.

We have successfully demonstrated that vaccination with type III-secreted proteins of E. coli O157:H7 can significantly reduce levels of this pathogen in cattle. This vaccine has now been licensed for use in Canada. Our current research is focused on the production of vaccination 13 strategies for Salmonella Enteritidis and C. jejuni in poultry. In addition the current E. coli vaccine is serotype specific and we are investigating the development of a vaccine for cattle that will be effective against non E. coli O157 STEC strains. The overall objective of enhancing a safe food production environment is to develop methods for detection of and intervention to reduce the hazard of disease in people living and working in the agricultural environment.

Research Objectives

The long term goal of this research project is to develop a family of animal vaccines which will reduce the levels of human bacterial pathogens in animals, thereby reducing the risk of human infection via contaminated food and water. More specifically, our research objectives include:

1. Characterization of non-O157 STEC isolates and determination of potential for cross-serotype protection using an E. coli O157:H7 vaccine based on Type III -Secreted Proteins (T3SP);
2. Optimization of formulation and delivery of the STEC vaccine for the induction of mucosal immunity in the intestine of cattle;
3. Determination of the role(s) of Salmonella Enteritidis Salmonella Pathogenicity Islands (SPI-1 and SPI-2) plus their effectors in colonization of chickens;
4. Identification of  additional surface exposed components of Salmonella Enteritidis involved in adhesion/invasion which might represent potential vaccine candidates;
5. Determination of their vaccine potential;
6. Identification of  antigens of C. jejuni which are involved in colonization of the chicken intestine;
7. Determination of the protective capacity of selected Campylobacter antigens;
8. Optimization of delivery of C. jejuni and Salmonella Enteritidis antigens to chickens;